diff --git a/modules/mesh-delivery-checker/internal/check/line.go b/modules/mesh-delivery-checker/internal/check/line.go
index 0882cf1..cedef15 100644
--- a/modules/mesh-delivery-checker/internal/check/line.go
+++ b/modules/mesh-delivery-checker/internal/check/line.go
@@ -2,6 +2,7 @@ package check
 
 import (
 	"fmt"
+	"slices"
 	"strings"
 	"unicode/utf8"
 
@@ -50,7 +51,7 @@ func firstFailed(v delivery.Verdict) string {
 
 // pieces are the parts of a line, from the most to the least needed.
 type pieces struct {
-	head, commits, counts, shortCounts, times, shortTimes, over, builds, composition, group string
+	head, commits, counts, shortCounts, times, shortTimes, over, builds, composition, shortComposition, group string
 }
 
 func (p pieces) join(drop int) string {
@@ -70,7 +71,10 @@ func (p pieces) join(drop int) string {
 	if drop < 2 && p.group != "" {
 		parts = append(parts, p.group)
 	}
-	if p.composition != "" {
+	switch {
+	case drop >= 3 && p.shortComposition != "":
+		parts = append(parts, p.shortComposition)
+	case p.composition != "":
 		parts = append(parts, p.composition)
 	}
 	out := make([]string, 0, len(parts))
@@ -90,14 +94,37 @@ func levelWords(name string, r delivery.LevelResult) string {
 	return s
 }
 
-func compositionWords(c *delivery.Composition) string {
-	switch {
-	case c == nil, c.State == delivery.CompositionNotRun:
+// compositionWords says the composition: not yet run, or once the assigner's check reports it (issue 1297) passed or
+// failed, with the time it took and the machines it composed (issue 1300).
+func compositionWords(c *delivery.Composition, took int64) string { return composition(c, took, false) }
+
+// composition is compositionWords; short counts the machines and leaves the SDK commit to the report.
+func composition(c *delivery.Composition, took int64, short bool) string {
+	if c == nil || c.State == delivery.CompositionNotRun {
 		return "composition not yet run"
-	case c.State == delivery.CompositionPass:
-		return "composition passed with " + short12(c.SDK)
 	}
-	return "composition failed: " + c.Words
+	in := ""
+	if took > 0 {
+		in = " in " + seconds(took)
+	}
+	on := ""
+	if len(c.Machines) > 0 {
+		machines := slices.Sorted(slices.Values(c.Machines))
+		on = " on " + strings.Join(machines, ", ")
+		switch {
+		case len(machines) > 1 && short:
+			on = fmt.Sprintf(" on %d machines", len(machines))
+		case len(machines) > 1:
+			on = fmt.Sprintf(" on %d machines: %s", len(machines), strings.Join(machines, ", "))
+		}
+	}
+	switch {
+	case c.State == delivery.CompositionPass && short:
+		return "composition passed" + in + on // the SDK it composed with is in the report
+	case c.State == delivery.CompositionPass:
+		return "composition passed" + in + " with " + short12(c.SDK) + on
+	}
+	return "composition failed" + in + on + ": " + c.Words
 }
 
 func buildWords(builds []BuildNote) string {
@@ -149,7 +176,7 @@ func parts(v delivery.Verdict, cs *Case, p Pull, builds []BuildNote, slowest []s
 		for _, x := range []struct {
 			name string
 			ms   int64
-		}{{"queue", t.Queue}, {"clone", t.Clone}, {"unit", t.Unit}, {"int setup", t.IntegrationSetup}, {"int run", t.IntegrationRun}, {"composition", t.Composition}} {
+		}{{"queue", t.Queue}, {"clone", t.Clone}, {"unit", t.Unit}, {"int setup", t.IntegrationSetup}, {"int run", t.IntegrationRun}} {
 			if x.ms > 0 {
 				times = append(times, x.name+" "+seconds(x.ms))
 			}
@@ -181,7 +208,8 @@ func parts(v delivery.Verdict, cs *Case, p Pull, builds []BuildNote, slowest []s
 	}
 	pc.builds = buildWords(builds)
 	if v.State != delivery.VerdictRunning {
-		pc.composition = compositionWords(v.Composition)
+		pc.composition = compositionWords(v.Composition, v.Took.Composition)
+		pc.shortComposition = composition(v.Composition, v.Took.Composition, true)
 	}
 	if cs != nil && len(cs.Pulls) > 1 {
 		pc.group = fmt.Sprintf("group %s of %d pull requests", cs.Group, len(cs.Pulls))
diff --git a/modules/mesh-delivery-checker/internal/check/line_test.go b/modules/mesh-delivery-checker/internal/check/line_test.go
index 6ea2499..662db1d 100644
--- a/modules/mesh-delivery-checker/internal/check/line_test.go
+++ b/modules/mesh-delivery-checker/internal/check/line_test.go
@@ -133,3 +133,24 @@ func TestThePassedCompositionIsSaidOnlyWhenItWasRun(t *testing.T) { // ADR 0484
 		t.Errorf("a verdict with no composition: %q", r)
 	}
 }
+
+func TestTheCompositionsTimeAndMachinesAreSaidOnceTheAssignerReportsThem(t *testing.T) { // 1300 (C10), the assigner's verdict (issue 1297)
+	cs, p := lineCase(t, pullOf(repoA, 7, head1))
+	v := passVerdict()
+	v.Took.Composition = 2400
+	v.Composition = &delivery.Composition{State: delivery.CompositionPass, SDK: "afbe371003a570f088be4a394d83aa7a9458f7ab", Machines: []string{"g14", "ace", "novox", "shanks"}}
+	r := Report(v, cs, p, nil, nil)
+	for _, want := range []string{"composition passed in 2.4s with afbe371003a5 on 4 machines: ace, g14, novox, shanks"} {
+		if !strings.Contains(r, want) {
+			t.Errorf("report %q lacks %q", r, want)
+		}
+	}
+	if l := Line(v, cs, p, nil, nil); !strings.Contains(l, "composition passed in 2.4s") || !strings.Contains(l, "on 4 machines") || utf8.RuneCountInString(l) > MaxLine {
+		t.Errorf("line = %q", l)
+	}
+	v.State, v.Failed = delivery.VerdictFail, delivery.FailedFirst{Machine: "novox", Words: "composition refused"}
+	v.Composition = &delivery.Composition{State: delivery.CompositionFail, Words: "novox: two seats claim dns", Machines: []string{"novox"}}
+	if r := Report(v, cs, p, nil, nil); !strings.Contains(r, "composition failed in 2.4s on novox: novox: two seats claim dns") {
+		t.Errorf("failed composition report = %q", r)
+	}
+}